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B Lüthi

Publications and source records attributed to B Lüthi.

15 recordsLinked to original sources
PubMed2001

Soft acoustic modes in the two-dimensional spin system SrCu2(BO3)(2).

SrCu2(BO3)(2) is a two-dimensional dimerized quantum spin system which is close to a quantum critical point. The sound velocity for the longitudinal and transverse acoustic modes shows strong spin-lattice effects. The shear c(66) mode exhibits a pronounced softening of 4.5% as a function of temperature and softens more than 25% in fields up to 50 T. This huge effect occurs in the vicinity of the magnetization plateaus m/m(0) = 1/4 and 1/3. We can analyze quantitatively the temperature dependence of all measured elastic modes c(11), c(44), and c(66) with an exchange striction mechanism. The soft c(66) mode with B(2g) symmetry enables us to predict the possible symmetry of the condensed triplets in some plateaus.

Journal Article↗
PubMed1977

[Biomechanics of vertebral segments. Clinical and prognostical interpretations (author's transl)].

The authors propose a new model to estimate the forces of the intrinsic equilibrium of the segment. Based on the theory of the so-called transient pole, it became possible to describe the momentary movement of an angle relative to its neighbour and to define the way of the intrinsic equilibrium. This transient pole fixes the centre of rotation around which the upper angle moves relative to the lower vertebral body. Normal and pathological cases can be diagnosed at once by use of a special röntgenological appliance in connection with the statistical experience. It becomes possible to calculate the forces and movements acting on a segment.

Biomechanical Phenomena↗